Terahertz photonic crystal quantum cascade laser coupled to a second order Bragg vertical extractor

Abstract

Surface emitting semiconductor lasers in the terahertz frequency range are highly demanded for spectroscopy, imaging, security and other applications. Due to their compactness and high power, Quantum Cascade Lasers (QCLs) are one of the most important laser sources in this region. The selection rule of intersubband transitions forces the radiation to be TM polarized and thus generated in-plane, consequently photonic structures have to be developed to extract the light vertically. Few approaches for surface emitting QCLs demonstrated the lasing of a second-order Bragg metallic grating patterned on top of a ridge or a surface emitting photonic crystal (PhC). PhC band-edge lasers with improved performance compared to Fabry-Perot lasers have already been reported. In this work a surface emitting band edge 2D PhC QCL is presented, using a second-order Bragg grating as a boundary condition. We show single mode devices operating around 3.1 THz with a maximum operating temperature of 125 K in pulsed operation, 100 K in CW, a farfield divergence of less than 20° or up to 12 mW of peak output power.